A conventional blasting system comprises a series of explosive charges which are detonated by detonators which are wired to a remote command source. In order to prevent breakage of the wiring connecting detonators set to go off late in the blasting by earlier explosions, the detonators are provided with delays, such that the last detonator to explode has received its firing signal prior to the explosion of the first. Recent improvements in the system have included electronic delays (replacing the older, less precise pyrotechnic delays), and the ability to program such delays in situ. German Offenlegungsschrift 3301251 provides an example of the versatility of which these systems are capable.
There has recently been provided in my co-pending Australian Patent Application Number PH1255 a detonator which comprises conditioning means which renders fusehead conductors incapable of carring a voltage or current capable of firing the detonator prior to the altering of the conditioning means from a "normal" (incapable of being fired) state to an "armed" state. This provides a considerable safety factor not previously present in detonators.